The party drug ketamine can have powerful beneficial effects on severely depressed patients who have struggled for years to recover, and the drug should be developed responsibly as a psychiatric medicine, British experts said on Thursday.

In a study published in the Lancet Psychiatry journal, specialists from Oxford University said there is an urgent need for ethical and innovative action by doctors to prescribe the drug under controlled conditions.

“We think patients’ treatment should be in specialist centers and formally tracked in national or international registries,” said Rupert McShane, a consultant psychiatrist and researcher at Oxford who has led a series of ketamine studies.

Ketamine is a licensed medical drug, widely used as an anesthetic and to relieve pain. But it is also used as a recreational drug - sometimes known as Special K - and can lead some people into addiction and drug abuse.

Several research teams around the world have been trialling ketamine use in chronic and recurring depression, since many patients with the psychiatric condition fail to respond to currently available antidepressants such as Prozac and Seroxat.

“I have seen ketamine work where nothing has helped before,” McShane said at a briefing in London.

The U.S. pharmaceutical company Johnson & Johnson is developing an intranasal form of the drug, called esketamine. Its results so far have been promising enough for Food and Drug Administration officials to award esketamine “breakthrough” status to speed its progress through regulatory hurdles.

McShane and his co-researcher Ilina Singh, a psychiatry professor at Oxford University, told the briefing there had been a worrying sharp rise in the past year in the number of private ketamine clinics in the United States.

There are wide variations in the clinical checks before a patient receives treatment, they said, and there is a need for clear guidelines and registries to track how patients respond.

Last month, the American Psychiatric Association issued a consensus statement on ketamine in a bid to guide safe, appropriate prescribing of the drug for severe patients who do not respond to regular antidepressants.

McShane stressed that the ketamine doses used in the Oxford depression treatment trials are given in controlled conditions and are very different from those taken by street or club users.

On the street, users often take several grams a day and can suffer severe bladder problems and impaired brain function. The doses used in medical trials are a fraction of that - around 80 milligrams - and given once a week in a monitored setting.

Singh said ketamine has such great potential to help a small group of very ill patients that it would be wrong not to find a way of allowing them to benefit from it: “This drug is available, it’s out there, and if we can help patients get treatment responsibly, it’s our duty to do so,” she said.

Treating patients in specialist centers should help doctors spot potential problems early, she said, as well as picking up any abuse problems with longer term use and narrowing down what dose, frequency, route and duration of treatment works best.